/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.nutch.microformats.reltag;

// Nutch imports
import java.nio.ByteBuffer;
import java.util.Collection;
import java.util.HashSet;

import org.apache.avro.util.Utf8;
import org.apache.hadoop.conf.Configuration;
import org.apache.nutch.indexer.IndexingException;
import org.apache.nutch.indexer.IndexingFilter;
import org.apache.nutch.indexer.NutchDocument;
import org.apache.nutch.storage.WebPage;
import org.apache.nutch.storage.WebPage.Field;
import org.apache.nutch.util.Bytes;

/**
 * An {@link org.apache.nutch.indexer.IndexingFilter} that adds <code>tag</code>
 * field(s) to the document.
 * 
 * @see <a href="http://www.microformats.org/wiki/rel-tag">
 *      http://www.microformats.org/wiki/rel-tag</a>
 * @author J&eacute;r&ocirc;me Charron
 */
public class RelTagIndexingFilter implements IndexingFilter {

	private Configuration conf;

	private static final Collection<WebPage.Field> FIELDS = new HashSet<WebPage.Field>();

	static {
		FIELDS.add(WebPage.Field.BASE_URL);
		FIELDS.add(WebPage.Field.METADATA);
	}

	/**
	 * Gets all the fields for a given {@link WebPage} Many datastores need to
	 * setup the mapreduce job by specifying the fields needed. All extensions
	 * that work on WebPage are able to specify what fields they need.
	 */
	@Override
	public Collection<Field> getFields() {
		return FIELDS;
	}

	/**
	 * Set the {@link Configuration} object
	 */
	public void setConf(Configuration conf) {
		this.conf = conf;
	}

	/**
	 * Get the {@link Configuration} object
	 */
	public Configuration getConf() {
		return this.conf;
	}

	/**
	 * The {@link RelTagIndexingFilter} filter object.
	 * 
	 * @param doc
	 *            The {@link NutchDocument} object
	 * @param url
	 *            URL to be filtered for rel-tag's
	 * @param page
	 *            {@link WebPage} object relative to the URL
	 * @return filtered NutchDocument
	 */
	@Override
	public NutchDocument filter(NutchDocument doc, String url, WebPage page)
			throws IndexingException {
		// Check if some Rel-Tags found, possibly put there by RelTagParser
		ByteBuffer bb = page.getMetadata().get(new Utf8(RelTagParser.REL_TAG));

		if (bb != null) {
			String[] tags = Bytes.toString(bb).split("\t");
			for (int i = 0; i < tags.length; i++) {
				doc.add("tag", tags[i]);
			}
		}
		return doc;
	}
}
